Method of manufacturing titanium



United States, Patent METHOD OF MANUFACTURING TlTANIUlVI James John Gray, Widnes, England, assignor to Imperial Chemical Industries Limited, London, England, a corporation of Great Britain No Drawing. Application March '14, 1957 Serial No. 645,930

Claims. (Cl. TS-84.5)

This invention relates to an improved process for the manufacture of metallic titanium.

It is well known that titanium can be produced by the reduction of titanium tetrachloride by suitable metals. In commercial practice both magnesium and sodium have been found to be effective reducing metals and commercial processes have been based on their use. These processes are normally carried out in such a manner as to yield a reaction product comprising the reducing metal chloride in the molten condition in which the desired metallic titanium is distributed. To recover the metal the reaction mass is normally cooled until the salt has solidified after which the whole mass is broken up and the solid dissolved by an aqueous leach preferably in a dilute aqueous acid. During this leaching step it is possible for the metallic titaniinn to pick up small amounts of deleterious elements, notably hydrogen and oxygen whose presence impairs to a very considerable extent the quality of the resulting titanium.

In British Patents 726,367 and 738,149 it has been proposed, in order to obtain titanium of desirable quality, to effect the leaching in an aqueous medium containing an oxidising agent. In commercial practice it has been found that the use of dilute hydrochloric acid containing a small quantity of nitric acid as an oxidant has resulted in the production of a metallic titanium of very high quality.

We have now made a surprising observation that provided that certain other conditions are observed, it is possible to obtain without the use of an oxidant in the leaching step, a titanium equal to if not better than the titanium resulting after an oxidation leach. The conditions which we have found governing for this purpose are the absence of free reducing metal in the reaction mass when the leaching is effected and a limited time of contact of the leaching solution with the reaction mass during at least the first stages of the leaching operation while maintaining continuous agitation of the system.

For the purpose of this invention the limited time of contact of leaching solution and reaction mass is 15 minutes but we prefer to maintain contact for a period of 3 to 5 minutes.

We have also found it advantageous to effect the reduction of titanium tetrachloride with slightly less than the stoichiometrical amount of metallic sodium thereby obtaining, after cooling, a solid reaction mass consisting of sodium chloride, metallic titanium and a small proportion of chlorides of titanium in which the average valency of the titanium is less than 4. It is thus an element in our invention that an excess of titanium tetrachloride is used in the basic reaction process. The solid product thus produced is reduced by conventional methods to a size suitable for the leaching operation and we have found it essential that the particles are less than inch in size. The ground product is then subjected to the action of aqueous acid, preferably hydrochloric acid of 0.5 to 2% concentration but it is an essential condition of our invention that the leaching operation as well as the subsequent withdrawal of aqueous acid should be carried out within a period of 15 minutes.

In a process for the manufacture of titanium by the reaction of titanium tetrachloride with metallic sodium and isolating the titanium therefrom the present invention comprises the improvement whereby a high quality titanium is obtained which comprises carrying out the said reaction in the presence of excess titanium tetrachloride, reducing the product to particles of less than inch size, leaching with dilute aqueous acid, removing the acidified solution and isolating the remaining titanium after washing with water, the steps of leaching and subsequent removal of acid solution being carried out within a period of 15 minutes.

In a preferred form of our invention we carry out a second leaching process, suitably using the same acid at the same concentration as in the first leaching. We prefer to carry out this second leaching within a period of 5 minutes and this step ensures that all soluble salts are removed from the titanium.

Finally the weak acid is removed and replaced by water which removes all traces of acid which adhere to the metal granules.

In the following examples which illustrate but do not purport to limit our invention the titanium-salt mixture to be leached was prepared by reacting titanium tetrachloride with metallic sodium 2% excess of titanium tetrachloride being present in the form of sub-chlorides of titanium. When reaction was complete the titanium-salt mixture was cooled to room temperature, removed from the reaction vessel and coarsely crushed to pass inch B.S.S. mesh. The mixture which then contained 20% by weight of titanium metal was finely ground to pass 10 B.S.S. mesh.

Example 1 Five parts by weight of the aforesaid ground titaniumsalt mixture were leached by stirring with 30 parts by weight of a 1% aqueous solution of hydrochloric acid for 15 minutes. The bulk of the acidified brine was then removed by decantation and the titanium powder washed by stirring again with 30 parts by weight of /2% hydrochloric acid solution for 15 minutes. Finally the titanium was washed with water until there were indications that the filtrate was substantially free from chlorine. The washed powder was then dried at 60 C. to give metal which was found to have a hydrogen content of 0.02% and, after arc-melting, a hardness of 148 D.P.N.

Example ll Five parts of the titanium-salt mixture containing 20% titanium were leached by stirring with 20 parts of a 1% aqueous solution of hydrochloric acid for 5 minutes. The bulk of the acidified brine was then removed by decantation and the titanium washed by stirring with a further 20 parts of 1% acid solution for 5 minutes. The titanium was then recovered by the method already described in Example I. The metal was found to have a hydrogen content of 0.003% and, after arc-melting, a harness of D.P.N.

What I claim is:

1. In a process for the manufacture of titanium by the reaction of titanium tetrachloride with metallic sodium and isolating the titanium therefrom, the improvement whereby a high quality titanium is obtained which comprises carrying out the said reaction in the presence of excess titanium tetrachloride, whereby a reaction product is obtained which contains titanium subhalide and is free of metallic sodium, reducing the reaction product to particles of less than inch size in any dimension thereof, prior to any water leach, leaching the thus reduced metallic sodium-free reaction product conacid, removing the acidified solution and isolating the remaining titanium after washing with water, the steps of acid leaching and subsequent removal of acid solution being carried out within a period of 15 minutes.

2. The improvement according to claim 1 in which the steps of acid leaching and subsequent removal of acid solution are carried out within a period of 3 to '5 min- IRES.

' 3. The improvement according to claim 1 in which following thesteps of acid leaching and subsequent removal of acid solution a second leaching with dilute hydrochloric acid is carried out to ensure complete withdrawal of soluble materials and the acidified solution is again removed.

4. The improvement according to claim 3 in which the second leaching and subsequent removal of acid is carried out in a period of less than 5 minutes.

5. The improvement according to claim 1 in which the hydrochloric acid solution used for leaching is of 0.5 to 2% acid concentration.

References Cited in the file of this patent UNITED STATES PATENTS 2,750,271 Cueilleron et al. June 12, 1956 

1. IN A PROCESS FOR THE MANUFACTURE OF TITANIUM BY THE REACTION OF TITANIUM TETRACHLORIDE WITH METALLIC SODIUM AND ISOLATING THE TITANIUM THEREFROM, THE IMPROVEMENT WHEREBY A HIGH QUALITY TITANIUM IS OBTAINED WHICH COMPRISES CARRYING OUT THE SAID REACTION IN THE PRESENCE OF EXCESS TITANIUM TETRACHLORIDE, WHEREBY A REACTION PRODUCT IS OBTAINED WHICH CONTAINS TITANIUM SUBHALIDE AND IS FREE OF METALLIC SODIUM, REDUCING THE REACTION PRODUCT TO PARTICLES OF LESS THAN 3/8 INCH SIZE IN ANY DIMENSION THEREOF, PRIOR TO ANY WATER LEACH, LEACHING THE THUS PREDUCED METALLIC SODIUM-FREE REACTION PRODUCT CONTAINING SAID TITANIUM SUBHALIDE WITH DILUTE HYDROCHLORIC ACID, REMOVING THE ACIDIFIED SOLUTION AND ISOLATING THE REMAINING TITANIUM AFTER WASHING WITH WATER, THE STEPS OF ACID LEACHING AND SEQUENT REMOVAL OF ACID SOLUTION BEING CARRIED OUT WITHIN A PERIOD OF 15 MINUTES. 